There are various applications in which it is necessary to be able to rapidly select particular items from a large number of other items, and to generate data which specifies a selected item, for input to an electronic data-processing system for example. When this item selection must be performed manually, i.e. by an operator actuating keys on a keyboard, or some other device, an excessive amount of time may be required, using conventional methods of item selection. One method which has been utilized to facilitate such item selection has been an item list in the form of a number of pages bound together like a book. Each page is perforated with an array of apertures, with an item appearing beside each aperture. In order to select a particular item, the page on which the item should appear is first looked-up. This page is then placed over a device having a set of keys each corresponding in position to an aperture on the page. The operator can then generate an electrical signal corresponding to the selected item by actuating the appropriate key. Alternatively, instead of an array of keys, an array of photoelectric elements may be employed, each corresponding in position to an aperture on the page. The operator in this case can generate an electrical signal specifying a particular item by applying a device such as a light pen to the appropriate aperture in the page.
Another method which has been employed in the prior art to rapidly specify selected items has been to use a single long rolled sheet, rather than a number of pages, with the array of perforations and the corresponding items thereon. The rolled sheet is wound around two rollers which are spaced apart, and pass beneath a transparent plate having an array of switches provided on its upper side. A motor can be actuated by the operator to drive the shafts such as to move the sheet until the desired item appears below the transparent plate. By actuating a corresponding switch, the operator can now generate an electrical signal designating the desired item.
The first of the methods described above, in which a number of pages are used bound in the form of a book, has the disadvantage that a large amount of time is required for the operator to look-up the appropritate page manually, then set the page in position for selection of the desired item. The second of the methods described above, in which a single long sheet is used in rolled form, has the disadvantage of a long look-up time, i.e. it may be necessary to unroll a large portion of the sheet in order to place a desired item below the selection switches. In addition, replacement of the sheet rolls will be difficult and time-consuming.
With the present invention, the disadvantages of prior art methods of looking up and selecting particular items, in order to generate a corresponding electrical signal, are overcome. The various items to be selected are provided on a number of pages. However, an appropriate page can be immediately selected by the operator actuating a corresponding page selection key on a keyboard. In this way, the long look-up time of a system employing a single long rolled sheet is avoided, while the time involved in manual look-up of a number of pages is also eliminated.